local content_cache = {}
function proc(http_header, url)
    if content_cache[url] then
        return content_cache[url]
    end
    local fp = assert(io.open("../extra/http-esvr/"..url, "rb"))
    local content = fp:read('*a')
    fp:close()
    content_cache[url] = content
    return content
end
return proc
